Do PET scans have a role in pretreatment evaluation?

On May 11 we noted a report on the potential value of MRI scans in clinical decision-making for prostate cancer patients prior to surgery. Today there is a new report on the potential of positron emission tomography (PET) compared to MRI in a similar (but not precisely the same) situation.

Watanabe et al. have carried out a direct comparison of two types of PET scan as well as MRI scanning in the pre-treatment detection of Japanese patients at risk for prostate cancer or scheduled for radical prostatectomy. The two different types of PET scan were 11C-choline PET (C-PET) and 18F-fluorodeoxyglucose PET (FDG-PET). MRI scans included unenhanced T1-weighted, unenhanced T2-weighted, and gadolinium-enhanced images.

Each of the three sets of imaging tests was carried out on 43 consecutive patients with suspected prostate cancer, and prostate cancers were histopathologically confirmed in 26 patients (presumably based on biopsy data). A nuclear medicine specialist reviewed the PET images and and a genitourinary radiologist reviewed the MRI images at random, and assigned a confidence level for the presence of prostate cancer for each patient, using a four-point scale.

The results of the analysis showed the following:

  • Sensitivity was significantly greater with MRI (88 percent) and C-PET (73 percent) images than with FDG-PET images (31 percent).
  • Accuracy was signifciantly greater with MRI images (88 percent) than with C-PET (67 percent) and FDG-PET (53 percent) images.
  • The area-under-curve value with MRI (0.90) was significantly greater than those with C-PET (0.53) or FDG-PET (0.54) images.

On the basis of this study, the potential role of currently available PET scans in the early work up of patients at risk for prostate cancer or scheduled for radical prostatectomy is limited compared to the potential role of MRI.

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